Process of treating sylvinite ores



Aug. 13, 1940. A J WEINIG 2,211,396

PROCESS OF TREATING SYLVINITE ORES Filed June 28, 1935 L/Vaf/ /vac/ Nac/@lem/M Cleaner Cleaner 3&1

a/numan, #fm @WMS Patented Aug. 13, 1940 UNITED sTTEs PROCESS F TREATINGSYLVINITE ORES Arthur J. Weinig, Golden, Colo., assignor to PotashCompany of America, Denver, Colo., a corporation of Colorado ApplicationJune 28, 1935, Serial No. 28,983

16 Claims.

This invention relates to a process for separating the soluble andvaluable constituents from sylvinite ores and the product or products tobe obtained by such process.

Sylvinite ore consists mainly of sodium chloride and potassium chloridecrystals, together with small amounts of other mineral matter, such asiron and manganese oxides, clays and the like. The sodium chloride andpotassium chloride crystals in the ore are found as distinct crystals,with a more or less amount of the two crystals intimately associatedtogether. Both are soluble in water, but with different rates ofsolubility with respect to the temperature of vthe solution. Both arefioatable by the froth otation process in a saturated water solution ofthe sylvinite ore, but each requires a different reagent or reagentcombination, to produce flotation. In the present invention advantage istaken of the differences in rate of solubility and flotation propertiesto effect a separation between the two salts.

'I'he object of the invention is to obtain potassium chloride in apractically pure form byl treating ore composed essentially of potassiumchloride, sodium chloride and various clays and other gangue matter in amethod employing a combination of iiotation and crystallizationtreatments. In this method the sodium chloride, with clays and othergangue matter, is rejected as a waste product.

Generally stated, the invention consists in forming a. saturatedsolution in water of the constituents of the ore, which mainly consistsof 3` sodium chloride and potassium chloride and introducing into thissolution the sylvinite ore in a nely divided condition, thus forming apulp,

and then separating the sodium chloride, as well as any gangue that maybe present, from the pulp o by flotation. The specific gravity of sodiumchloride is 2.2, while the specific gravity of potassium chloride is 2.,-and in order to float ofi' the sodium chloride a selective reagent orreagents is or are employed to cause air bubbles, produced in thesolution in any suitable manner, to float the sodium chloride to thesurface of the solution without affecting the potassium chloride, or ifaffecting it, to retard or depress any dotation thereof. 'Ihe reagentemployed consists of any fatty acid or as the equivalent thereof aderivative of a fatty acid or mixture thereof which is capable of beingdissolved in the saturated brine solution employed, together with leadand/or bismuth salts, also dissolved in the saturated solution. It is tobe particularly pointed out, as indicated above, that the fatty acids orderivatives of fatty acids employed must be such as are capable of beingdissolved in the saturated solution of the ore, such for example ascocoanut oil soap and palm kernel oil soap. There are certain fattyacids and derivatives of fatty acids which are insoluble in such asolution, and such are not included inthe class of fatty acids orderivatives of fatty acids to be employed as a reagent. But it is to beexpressly understood that the term f atty acids as used in thisdescription and in the claims is intended to include not only fattyacids strictly as such but also any derivative or derivatives of fattyacids which are soluble in a saturated solution of sodium l@ chlorideand potassium chloride. Furthermore, when a straight saturated solutionof potassium chloride and sodium chloride has its temperature reduced,potassium chloride crystallizes out, but when lead and/or bismuth saltsare present in 0 the saturated solution, potassium chloride will notcrystallize out of the solution, even with material cooling of thesolution, unless potassium chloride in solid form is present in thesolution to act as seed," and even then the potassium chloridecrystallizes only on the seed and not on the surface of pipes,containers and other parts. The result of thisis that clogging of thepipes, etc. is avoided by the presence of the lead and/or bismuth saltsin the solution. Another advantage lies in the fact that such saltsalmost entirely prevent corrosion of iron surfaces by the brinesolution.

When potassium chloride and sodium chloride are dissolved in water atapproximately 70 F., in the presence of sylvinite ore, the amount ofsodium chloride passing into solution greatly exceeds that of thepotassium chloride, so that when the saturated solution is obtained itis what may be appropriately termedva brine or salt solution, and it isthis saturated solution that is preferably employed in the initialotation of the sodium chloride. It will be understood that inasmuch asthe water solution in which the finely divided particles of thesylvinite ore are deposited is a saturated solution containing dissolvedlead or bismuth, the ore thus deposited in the solution remains in solidform, and the mixture of this solution and the finely divided oreconstitutes, and will hereinafter be, referred to as, the pulp.

The flotation step may be carried out in any suitable flotation cell,and preferably it is carried out in a plurality of such cells associatedtogether in series, in which cells the ratio of ore to solution may bevaried. Thus. in the first flotation cell a large portion of the sodiumchloride, and gangue if present, may be oated out while still leaving inthe pulp some of the sodium chloride, and this is removed by arepetition of the flotation process in the succeeding cells to the endthat the pulp passing from the final cell is a nearly pure potassiumchloride in solid form carried by the saturated solution, together withsmall quantities of iron oxide and manganese oxide.

Furthermore, it has been found that the flotation froth passing from theseveral flotation cells carries not only sodium chloride (in solid form)but also more or less of potassium chloride (likewise in solid form),and in order to effect a complete recovery of the potassium chloride, itis necessary that this potassium chloride, associated with the sodiumchloride froth, be also recovered.

If the temperature oflthe saturated solution carrying the sodiumchloride froth with its associated potassium chloride be raised, theamount of potassium chloride that will be dissolved in the heatedsaturated solution will be largely increased over that dissolved at alower temperature, whereas the amount of sodium chloride that will becarried by such heated solution will be decreased. Advantage is taken ofthis to pass the potassium chloride that is thus associated with thesodium chloride in the flotation froth into solution and afterwards torecover the same from this enriched solution. To this end the saturatedsolution carrying the sodium chloride froth from the flotation cells isrst heated under agitation, and then While still heated, sodium chlorideis permitted to settle out of the solution, and after separating thesettled sodium chloride from the solution, the solution is cooled in thepresence of solid potassium chloride otherwise obtained in the practiceof the' process. The solid potassium chloride affords seed upon whichpotassium chloride carried in the heated solution, referred to above,will crystallize out upon cooling, and such solidV potassium seed may bederived from the flotation cells or otherwise. The result of thisprocedure is that very nearly all of the potassium chloride contained inthe sylvinite ore under treatment is recovered.

The sodium chloride that settles out of the heated solution andseparated, as indicated above, may be purified and freed from moisture,and is then ready for sale or other disposition.

The potassium chloride sludge, which is the pulp remaining from theabove sodium chloride flotation and is freed from the sodium chloride,

has the liquidi separated therefrom in any suitable dewaterer, whichliquid, with more or less finely divided solid potassium chloride, ispassed to a potassium chloride thickener, While thebody of the thickenedsludge from the dewaterer combined with the settled solids from thethickener is transferred to a centrifuge where the remaining solution isremoved, the solid potassium chloride washed and prepared for drying.

The several steps of the process above described will be best understoodfrom a reference to the accompanying ow sheet which is, in effect, aplan view of a milling operation embodying the process of my invention.Reference numeral I indicates a grinding mill, which is preferably apebble mill, it being essential to avoidl any class of grinding millsthat present polished iron surfaces, since the lead or bismuth in thesaturated solution wouldbe precipitated out of the solution ii' broughtin contact with polished iron surfaces; 2 indicates a suitable hopperfor delivering the ore to the mill, and 3 indicates a tank containingthe saturated solution of sylvinite ore from which tank the solution istransferred through conduits indicated by the dotted ,linea to theseveral flotation cells and other parts of the apparatus, including thepebble mill I. The crushed ore from the pebble mill is delivered,preferably by a pump 4. to any suitable classifier 5 where the finerparticles suitable for treatment in the flotation process are separatedfrom the coarser particles, which latter are returned from theclassifier to the mill I through the hopper 2, while the finer particlesare delivered to the initial notation cell 6, where, being mixed withthe saturated solution of constitutients of the sylvinite ore, they forma pulp. Suitable reagents in the form of fatty acids or derivatives offatty acids that are soluble in the saturated solution are added to thesaturated solution at any suitable point, as well as lead and/or bismuthsalts. The amounts of the reagents may vary under different conditions,but it has been found that about four pounds of the fatty acid or derivatives of fatty acids per ton of ore treated is usually required whenthe solution contains about two pounds of dissolved lead and/or bismuthper ton of the solution. These reagents are freely dissolved in thesolution, and during thepractice of the process the fatty acid orderivatives of fatty acid will be more or less consumed and additionswill have to be made thereto, but the lead and/or bismuth remainsunconsumed except for a very slight loss that is carried off in thesaturated solution that adheres as moisture to the concentrate. Thisslight loss is taken care of by suitable additions. As a matter ofpractice the main part of the reagent is added to the saturated solutionin the flotation cell 6, but other additions may be and generally aremade at other points as hereinafter referred to. There may be, andpreferably there are, a plurality of such original flotation cells, asshown for example at 6 and 6. These flotation cells 6 and 6' areprovided with suitable agitators whereby, with proper introduction ofair, bubbles are formed in the pulp, and the effect of the reagents isto cause the sodium chloride to adhere to the bubbles which rise to thesurface and are floated of! in the shape of froth into the flotationtrough 6". It has been found that the froth thus delivered from theflotation cells 6 and 6' carries with it not only solid sodium particlesbut also the gangue material of the ore and some of the solid particlesof potassium chloride, and therefore, in order to effect a maximumrecovery of all of the potassium chloride in the ore, steps are taken toseparate this potassium chloride from the sodium chloride froth. To thisend the froth is passed into one or more, and preferably a series (hereshown as three) of so-called cleaner cells `I-'I, arranged in series,which cells operate on identically the same principle as the originalflotation cells 6 and 6', floating oi the sodium chloride in the form offroth into the froth trough 1', to the end that the froth thus deliveredfrom the last cleaner cell 'I is substantially free from potassiumchloride, except certain small particles of potassium chloride andsodium chloride which are intimately associated together.

The pulp remaining in the original flotation cells 6 and 6', after thesodium chloride has been floated therefrom, is passed from the cells 6,6

directly to cells technically known as middling cells. This pulp iscomposed largely of theV saturated solution and potassium chloride, but

there are almost invariably small particles of sodium chloride attachedto particles of potassium chloride and these attached particles arefloated to the surface in the cell 3 and delivered into the trough 8'.,additional reagents. being added at the cell 8. From the trough 3' thefroth is delivered to any suitable dewaterer 3. where the saturatedsolution is to a very large extent separated from the solid particles.these particles being delivered to the hopper 2 to be reground, whilethe solution is delivered through the pump I to the classifier andreturns to the system.

The sodium chloride froth, with small particles of potassium chlorideattached thereto or intimately associated therewith, and which has beenpassed to the cleaner cells 1 is delivered from the last one of thecells I to a container IIl provided with means for heating its contentsand also with means for agitating the same. This is technically known asa heating agitator. The sodium chloride froth with the accompanyingpotassium chloride particles carries with it, of course, more or less ofthe saturated solution but it may be and frequently is desirableto'supply an additional amount of the saturated solution to the heatingagitator, and this is accomplished by withdrawing such saturatedsolution from the stock tank 3 through conduits, indicated by Iii) Thepulp from the heating agitator is thenl passed directly into thecontainer II where it is maintained free from agitation, and the sodiumchloride is thus permitted to settle out. The temperature of the pulp ismaintained in the container i I at approximately the same as thetemperature in the heating chamber Ill so that the potassium chlorideremains in solution, and only sodium chloride settles out.

Referring now to the so-called middling cells B, the pulp from thosecells, the solid part of which is practically pure potassium chloride,is passed directly therefrom to a cooling agitator I2, where thetemperature is lowered to approximately that of the entire system otherthan that in the tanks I and Ii. The sodium chloride solids having beensettled out of the heated solution in the thickener tank II andseparated therefrom, this solution is also passed into the coolingagitator where it comes in' contact with the particles of potassiiunchloride that have been delivered thereto from the middling flotationcells il, which particles act as seed upon which the potassium chloridein the solution from the thickener tank II crystallizes as the result ofthe drop in temperature in the cooling tank, the contents of this tankbeing agitated during the operation. A further result of the lowertemperature in the cooling agitator I2 ising to the dewaterer I3,- ashereinafter described,

consists of approximately pure potassium chloride.

From the cooling agitator I2 the pulp is pass to a dewaterer I3 in whichthe saturated soluti n is largely removed from the potassium chloridesolids and then passed to a potassium chloride thickener Il. Thissaturated solution thus re moved from the dewaterer and passed to thethickener I4 will carry more or less fine particlestank 3.

From the dewaterer I3 and the thickener Il the potassium chloride solidshaving a small amountv of solution associated therewith, is

. passed to a centrifuge I5 wherein the remaining amount of the solutionis removed and passes by way of the container Il to the vstock tank 3.The centrifuging removes nearly all of the saturated solutionaccompanying the potassium chloride, but there remains a very smallamount of suchA solution attached to the patassium chloridel particles,and this solution contains sodium chloride which it is essential toremove from the potassium chloride particles, if the potassium chlorideisto be entirely free from sodium chloride. Accordingly, the centrifugedpotassium chloride particles are submitted to a washing operation andthus freed from the sodium chloride contained in the original solution.To accomplish this washing without loss of any potassium chloride, andto assure the removal of the sodium chloride, the solids in thecentrifuge I5 are washed with a saturated solution of potassiumchloride. If perchance there are any stray particles of sodium chloridewith the potassium chloride in the centrifuge IE, this saturatedsolution of potassium chloride will dissolve them without dissolving anyof the potassium .chloride, and furthermore the saturated solution ofthe potassium chloride acts as the means of washing the potassiumchloride in the centrifuge free from any of the original solution whichcontains sodium chloride. If desired, water may be used as the washingmedium, in which case, the water will become saturated with potassiumchloride shortly after it comes in contact with the material. Thiswashing is preferably effected in the centrifuge IE, and this washingsolution, as well as any of the original saturated solution, passes fromthe centrifuge I5 to the thickener I4 where any solid potassium chlorideis settled out and the solution is then returned to the system by way ofthe stock tank 3.

While as illustrated in the flow sheet, the heating agitator I0 is shownas separate from the cleaner cells 1, this heating of the pulp may, ifdesired, be effected in one or more of the cleaner cells 1. Moreover, itwill be recognized that inasmuch as the middlings flotation cells 8 areat a lower temperature than that maintained in the heating agitator (orif preferred, in the heated cells l), the overflow from the sodiumchloride thickener Ii may be discharged directly into the middlingsflotation cells 8, where the function above indicated as pertaining vtothe cooling agitator I2 will take place, in which case it will beunderstood that cooling means will be provided in connection with themiddlings flotation cells 8, vfrom which cells the potassium chloridesolids with the saturated solution is passed directly to the dewatererI3.

While the invention has been described m connection with a ow sheet,setting forth in detail certain -arrangement of the notation cells,heating and cooling agitators, thickeners, etc.. it will be appreciatedby one skilled in the art that various changes and modifications in thearrangement thereof may be made without departing from the spirit of theinvention as herein set forth, and it will be understood that such,

flow sheet is merely for the purpose of illustrating the invention, andnot for the purpose of defining the limits thereof, reference being hadto the appended claims for this purpose.

It will also be understood that fatty acids, and derivatives of fattyacids, as well as mixtures of these -are equivalents, provided only thatthey are soluble in a saturated solution of the sylvinite ore, and theterm fatty acid used in the claims is intended to include any and allsuch derivatives and mixtures.

It will also be understood that, if desired, the ore may be subjected todry grinding and the product of such grinding then introduced into asaturated solution of the ore.

It will be found that the potassium chloride secured as the result ofthe process herein described is not the ordinary white, chemicallyrefined potassium chloride. On the contrary, it is granular in form andof a pinkish color due to small amounts of iron oxide and manganeseoxide in the sylvinite ore and which remain with and color the potassiumchloride obtained as a product. This is a product never heretoforeproduced and constitutes a new result achieved by combining the steps ofthe process herein set forth. One of the important uses of the potashproduced by this invention is'in fertilizers, and the iron and manganeseoxides are of value therein, and the particular form and coloring affordmeans as identifying the product of this process.

Where the expression containing dissolved lead is used in the claims, itis intended to designate the presence of either lead or bismuth insolution, or any or all equivalents and mixtures of the typehereinbefore described.

The invention here described and claimed utilizes the principle ofselective flotation of sodium chloride forming the subject-matter of mycopending application filed November 8, 1937, Serial No. 173,431 and ofwhich one example is the subject-matter of my prior Patent 2,105,295January 11, 1938.4 Features of the entire process disclosed but notclaimed herein form the subject-matter of my copending application iiledMay 25, 1936, Serial No. 81,729.

Having thus described the invention, what .is claimed is:

1. In a cyclic process of treating sylvinite ores, the steps ofintroducing sylvinite ore in finelydivided condition into a saturatedsolution of the ore, containing dissolved lead, to form a pulp, removinggangue and a substantial part of the sodium chloride from the pulp in aninitial froth flotation treatment in the presence of a reagent having aselective alnity for sodium chloride and gangue, and purifying thepotassium chloride in the non-floated residue of said flotationtreatment by a second froth dotation treatment in the presence of areagent having a selective aiinity for sodium chloride and returning theresulting sodium chloride froth to the cycle for reworking Aandremoval'in the initial flotation treatment.

2. In a cyclic process of treating sylvinite ores, the steps of:introducing sylvinite ore in finelydivided condition into a saturatedsolution of the ore, containing dissolved lead, to form a pulp, removinggangue and a substantial part of the sodium chloride from the'pulp in aninitial frothl notation treatment in the presence of a reagent 5 havinga selective amnity for sodium chloride and gangue, and purifying thepotassium chloride in the non-floated residue of said flotationtreatment by a second froth flotation treatment at a controlledtemperature, in the presence of a reagent having a selective affinityfor sodium chloride and returning the resulting suitably cooled sodiumchloride froth to the cycle for reworking and removal in the initialflotation treatment. l5

3. In a process of treating sylvinite ores, the steps of introducingsylvinite ore in finelydivided condition into a saturated solution ofthe ore, containing dissolved lead, to form a pulp, removing gangue anda substantial part of the zo sodium chloride from the pulp in an initialfroth flotation treatment in the presence of a reagent having aselective afiinity for sodium chloride and gangue, mixing the residue ofthe initial flotation with a saturated sodium chlolride, potassiumchloride solution at a lower temperature than the residue, and purifyingpotassium chloride in the mixture by a second froth flotation treatmentin the* presence of a reagent having a selective afllnity for sodiumchloride to thereby remove the remaining sodium chloride as a frothconcentrate.

4. In a cyclic process of treating sylvinite ores, the steps ofintroducing sylvinite ore in finelydivided condition into a saturatedsolution of the ore, containing dissolved lead, to form a pulp, removinggangue and a substantial part of the sodium chloride from the pulp in aninitial froth flotation treatment in the presence of a reagent having aselective ailinity for sodium chloride 40 and gangue, purifying thepotassium chloride in the non-floated residue of said flotationtreatment by a second froth flotation treatment in the presence of areagent havinga selective ailinity for sodium chloride, and separatingpotassium chloride and sodium chloride constituents of the frothconcentrate of the initial flotation in a cleaner circuit in thepresence of a reagent having a selective aiinity for sodium chloride andgangue, said cleaner circuit returning 60 the non-floated residue to thecycle for reworking and separation in the initial flotation treatment.

5. In a cyclic process of treating sylvinite ores, the steps ofintroducing sylvinite ore in finelydivided condition into a saturatedsolution of the ore, containing dissolved lead, to form a pulp, removinggangue and a substantial part of the sodium chloride from the pulp in aninitial froth otation treatment in the presence of a reagent having aselective anity for sodium chloride and gangue, purifying the potassiumchloride in the non-oated residue of said notation treatment by a secondfroth flotation treatment in the presence of a reagent having aselective amnity for sodium chloride, and separating potassium chlorideand sodium chloride constituents of the froth concentrate of the initialflotation in a cleaner circuit at a controlled temperature, in thepresence of a reagent having a selective aflnity for sodium chloride andgangue, said cleaner circuit returning the suitably heated non-floatedresidue to the cycle for reworking and separation in the initialflotation treatment.

6. In a process of treating sylvinite ores, the

stepsof introducing sylvinite ore in finely-di- 76 vided condition intoa saturated solution of the oreI containing dissolved lead, to form apulp. removing gangue and a substantial part of the sodium chloride fromthe pulp in an initial froth flotation treatment in the presence of areagent having a selective affinity for sodium chloride and gangue,mixing the froth concentrate of the initial flotation' with a saturatedsodium chloride, potassium chloride solution at a lower temperature thanthe concentrate, and separating potassium chloride and sodium chlorideconstituents of the mixture in a cleaner circuit in the presence of areagent having a selective amnity for sodium chloride and gangue.

7. In a cyclic process of treating sylvinite ores, the steps ofintroducing sylvinite ore in finelydivided condition into a saturatedsolution of the ore, containing dissolved lead, to form a pulp, removinggangue and a substantial part of the sodium chloride from the pulp in aninitial froth flotation treatment in the presence of a reagent having aselective afilnlty for sodium chloride and gangue, purifying thepotassium chloride in the non-floated residue of the said flotation Vtreatment by a second froth flotation treatment in the presence of areagent having a selective aflinlty forsodium chloride to thereby removethe remaining sodium chloride as a frothconcentrate, separating thepotassium chloride and sodium chloride of the froth concentrate of theinitial flotation in a cleaner circuit in the presence of a reagenthaving a selective aillnity for sodium chloride and gangue, andreturning the froth of the second flotation, and the tailings of thecleaner circuit to the feed of the initial flotation.

8. In a cyclic process of treating sylvinite ores,

l the steps of introducing sylvinite ore in finelydivided condition intoa saturated solution of the ore, containing dissolved lead, to form apulp, removing gangue and a substantial part of the sodium chloride fromthe pulp in an initial froth flotation treatment in the presence of areagent having a selective aillnity for sodium chloride and gangue,purifying the potassium chloride in the non-floated residue of the saidflotation treatment by a second froth flotation treatment in thepresence of a reagent having a selective affinity for sodium chloride tothereby remove the remaining sodium chloride as a froth concentrate,separating the potassium chloride and sodium chloride of the frothconcentrate of the initialflotation in a cleaner circuit in the presenceof a reagent having a selective afilnity for sodium chloride and gangue,and returning the froth of the second flotation to the feed of Y theinitial flotation.

9. In a cyclic process of treating sylvinite ore the steps ofintroducing sylvinite ore in finelydivided condition into a saturatedsolution of the ore, containing dissolved lead, to form a pulp, removinggangue and a substantial part of the sodium chloride from the pulp in aninitial froth flotation treatment in the presence of a reagent having aselective affinity for sodium chloride and gangue, purifying thepotassium chloride in the non-floated residue of the said flotationtreatment by a second froth flotation treatment in the presence of areagent having a selective ailinity for sodium chloride land gangue tothereby remove the remaining sodium chloride as a froth concentrate,separating the potassium chloride and sodium chloride of the frothconcentrate of the initial flotation in a cleaner circuit in thepresence of a, reagent having a selective affinity for sodium chlorideand gangue, and returning the tailings of the cleaner circuit to thefeed of the initial flotation.

10. In a cyclic process of treating sylvinite ores for-the recovery of apurified potassium chloridefp'oduct, the steps of introducing sylviniteore in finely-divided condition into a saturated solution of the ore,containing dissolved 4 lead, to form a pulp. removing gangue `and afinely-divided condition into a saturated solution of the ore,containing dissolved lead, to form a pulp, removing gangue and asubstantial part of the sodium chloride from the pulp in an initialfroth flotation treatment in the presence of a reagent having aselective aillnity for sodium chloride and gangue, purifying thepotassium chloride in the non-floated residue of said flotationtreatment by a second froth flotation treatment in the presence of areagent having a selective affinity for sodium chloride to therebyremove the remaining sodium chloride as a froth lconcentrate, andreturning the froth of the second flotation treatment to the initialtreatment stage.

12. In a cyclic process of treating sylvinite ores, the steps ofintroducing sylvinite ore in finely-divided condition into a saturatedsolution of the ore, 'containing dissolved lead, to form a pulp,removing gangue and a substantial 'part of the sodium chloride from thepulp in an initial froth flotation treatment in the presence of areagent having a selective ailinity for sodium chloride and gangue,purifying vthe potassium chloride in the non-floatedv residue of saidflotation treatment by a second froth flotation treatment in thepresence of a reagent havingv a selective affinity for sodium chlorideto thereby remove the remaining sodium chloride as a froth concentrate,returning the froth of the second flotation treatment to the initialtreatment stage, and removing the non-floated residue of the secondflotation treatment separately from the froth. v

13. In a cyclic process of treating sylvinite ores, the steps ofintroducing sylvinite ore in finely-divided condition into a saturatedsolution Vin the presence of a reagent having a selective afllnity forsodium chloride and gangue.

14. In a process of treating sylvinite ores, including wet grinding ofsylvinite ore in a saturated sodium chloride, potassium chloridesolution, the improvement which comprisesv introducing a saturatedsodium chloride, potassium chloride solution into the grinding operationat a lower temperature than the mill discharge to prevent undue rise intemperature in the pulp occasioned by the grinding action.

15. In a process of treating sylvinite ores, including wet grinding ofsylvinite ore in a saturated sodium chloride, potassium chloridesolution containing lead, the improvement which comprises introducing a.saturated sodium chloride, potassium chloride solution into the grindingoperation at a lower temperature than the mill discharge to preventundue rise in tempera-

